1. Field of the Invention
The present invention relates generally to cellular mobile communication systems, and more particularly to a communications system in which cell-site base stations are connected via an ISDN (integrated services digital network) to one of mobile telephone switching systems.
2. Description of the Related Art
In a cellular communication system in which cell-site base stations and mobile telephone switching offices (MTSO) are connected to an ISDN, each of the MTSOs is associated with a corresponding group of the base stations so that mobile calls from the base stations of the same group are all routed to the corresponding MTSO. Because of the different incoming traffic patterns of cell-site groups, the MTSOs have different capacities for handling outgoing calls. As a result, some of the MTSOs where incoming calls account for a substantial proportion of their capacity, they are excessively overloaded with outgoing calls from the corresponding base stations. Because of the one-to-one correspondence between the cell-site groups and the MTSOs, the outgoing traffic patterns of the MTSOs cannot be altered according to their incoming traffic patterns.
To solve this problem, a proposal has been made in the EIA Interim standard Cellular System Mobile Station-Land Station Compatibility Specification 15-3-d, March 1987, that a request for call should be denied if an MTSO is overloaded. However, since this denial approach is performed without taking account the traffic patterns of the other MTSOs which are connected to the same ISDN, it does not represent the fundamental solution.